Name ____________________________________ Date __________ Class ___________________
17
WATER AND AQUEOUS SYSTEMS
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SECTION 17.1 LIQUID WATER AND ITS PROPERTIES (pages 475–478)
This section explains the hydrogen bonding that occurs in water molecules and how high surface
tension and low vapor pressure can be explained in terms of hydrogen bonding.
The Water Molecule (pages 475–476)
1. What unique molecular compound is the foundation of all life on Earth?
water
________________________
3/4
2. Approximately what fraction of Earth’s surface is covered in water? ___________
3. Circle the letter next to each sentence that is true concerning water molecules.
a. Each O — H covalent bond in a water molecule is nonpolar.
b. In a water molecule, the less electronegative hydrogen atoms acquire a
slight positive charge and the oxygen atom acquires a slight negative
charge.
c. Because the water molecule has an H — O — H bond angle of 105°, the
molecule as a whole is polar.
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4. The diagram below depicts a water molecule. Complete the labels showing the
locations of the hydrogen atoms, the oxygen atom, and the regions of positive
and negative charge.
oxygen
(or O)
hydrogen
(or H)
hydrogen
(or H)
5. List five important properties of water that result from hydrogen bonding.
a.
b.
c.
d.
e.
high surface tension
low vapor pressure
high specific heat capacity
high heat of vaporization
high boiling point
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CHAPTER 17, Water and Aqueous Systems (continued)
6. The diagram below depicts a collection of water molecules. Draw dotted lines
showing where hydrogen bonding occurs.
Surface Properties (pages 476–477)
7. Circle the letter next to each sentence that describes a result of the surface
tension of water.
a. In a full glass of water, the water surface seems to bulge over the rim of the
glass.
b. Water beads up into small, nearly spherical drops on a paper towel.
c. Water forms nearly spherical drops at the end of an eyedropper.
d. An insect called a water strider is able to “walk” on water.
8. Using Figure 17.5 on page 477, explain why a water drop has surface tension.
Because water molecules at the surface cannot form hydrogen bonds with air
molecules, molecules on the surface are drawn into the body of liquid. The inward pull
on the molecules is surface tension.
10. Circle the letter next to each sentence that correctly describes a property of
detergents.
a. Detergent molecules interfere with hydrogen bonding between water
molecules.
b. Detergent molecules strengthen hydrogen bonding between water
molecules.
c. Detergents act as “wetting agents.”
d. When detergents reduce surface tension, beads of water collapse and the
water spreads out.
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9. What geometric shape has the smallest surface area for a given volume?
a sphere
________________________
Name ____________________________________ Date __________ Class ___________________
11. Do liquids that have higher surface tension produce drops that are flatter or
more nearly spherical than liquids with lower surface tension?
Liquids with higher surface tension produce drops that are more nearly spherical.
12. What is the name for an agent, such as a detergent, that has the ability to
surfactant
reduce surface tension? ________________________
Specific Heat Capacity (page 478)
hydrogen
13. The high specific heat capacity of water is due to ________________________
bonding.
14. Is the following sentence true or false? Iron requires nearly 10 times more heat
than an equal mass of liquid water to produce the same temperature increase.
false
____________________
15. What effect does a large body of water have on the daily temperature of the air
around it?
It moderates the temperature by keeping it cooler during the day and warmer
at night.
SECTION 17.2 WATER VAPOR AND ICE (pages 479–481)
This section explains why water has a high heat of vaporization and a high boiling point. It also
explains why ice floats on liquid water.
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Evaporation and Condensation (pages 479–480)
1. Is the following sentence true or false? Because of hydrogen bonding, water
absorbs a large amount of heat as it evaporates or vaporizes.
true
____________________
2. Circle the letter next to each sentence that is true about vaporization or
condensation of water.
a. An extensive network of hydrogen bonds tightly holds the molecules in
liquid water together.
b. Hydrogen bonds continue to exist between water molecules in the vapor
state.
c. Because liquid methane has no hydrogen bonding, its heat of vaporization
is higher than that of water.
d. The amount of heat given off during the condensation of one gram of water
is the same as the amount of heat absorbed by one gram of water when it
vaporizes.
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CHAPTER 17, Water and Aqueous Systems (continued)
3. How are the evaporation and condensation of water important to regional
temperatures on Earth? Temperatures in the tropics would be much higher if water
did not absorb heat while evaporating from the surfaces of surrounding oceans.
Temperatures in polar regions would be much lower if water did not release heat while
condensing out of air.
4. Look at Table 17.1 on page 480, which shows several substances with low
molar mass. What is unusual about the boiling point of water? How can this
difference be explained? Water has a boiling point that is substantially higher than
the other compounds. Because of hydrogen bonding in water, more heat is needed
to disrupt attractions between water molecules.
Ice (pages 480–481)
5. What happens to the density of most substances as they cool and solidify?
Density usually increases as a substance cools.
6. The diagrams below show hydrogen bonding in water molecules.
Hydrogen
bonds
(ii)
(i)
a. Which diagram depicts ice? _______
(ii)
b. Which diagram depicts liquid water? _______
c. Why is ice less dense than liquid water? Refer to the diagrams to help you
explain. Ice molecules are arranged in an open rigid framework as shown in
diagram (i). When ice melts, the framework collapses, as shown in diagram (ii),
and the molecules pack closer together.
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(i)
Name ____________________________________ Date __________ Class ___________________
7. Look at Table 17.2 on page 480. To four significant figures, list the density of
1.000 g/cm3
a. liquid water at 4 °C ___________________
0.9998 g/cm3
b. liquid water at 0 °C ___________________
c. ice at 0 °C
0.9168 g/cm3
___________________
8. What is unusual about the data in Question 7? Will ice float on liquid water?
The density of liquid water decreases from 4 °C to 0 °C, and ice at 0 °C is less dense
than liquid water at 0 °C. Yes, ice will float on liquid water.
SECTION 17.3 AQUEOUS SOLUTIONS (pages 482–488)
This section describes the process of solvation; distinguishes among strong electrolytes, weak electrolytes, and nonelectrolytes; and explains water of hydration.
Solvents and Solutes (page 482)
1. Water samples containing dissolved substances are called
aqueous solutions
_______________________________
.
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Match each term to its description by writing its letter on the line next to the
description.
c
_______
2. dissolving medium
a. solution
b
_______
3. dissolved particles
b. solute
a
_______
4. homogeneous mixture of particles in a
dissolving medium
c. solvent
5. Is the following sentence true or false? After sodium chloride dissolves in a
container of water, the sodium chloride will eventually settle to the bottom of
the container if the solution remains undisturbed at a constant temperature.
false
____________________
6. Circle the letter next to each sentence that is true about aqueous solutions.
a. Solute particles can be either ionic or molecular, and their average
diameters are usually less than 1.0 nanometers.
b. When a solution is filtered, both solute and solvent will pass through the
filter paper.
c. Ionic compounds and substances containing polar covalent molecules
readily dissolve in water.
d. Nonpolar covalent molecules, such as those found in oil, grease, and
gasoline, readily dissolve in water.
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CHAPTER 17, Water and Aqueous Systems (continued)
7. Is the following sentence true or false? Solvents and solutes may be gases,
true
liquids, or solids. ____________________
The Solution Process (page 483)
8. When a solid crystal of sodium chloride is placed in water, what happens?
Water molecules collide with the crystal and attract its Na+ and Cl– ions.
9. What process occurs when solute ions become surrounded by solvent
solvation
molecules? _________________________
10. Look at the model of solvation in Figure 17.12 on page 483. If there is enough
solvent, what will eventually happen to the ionic solid depicted on the left side
of the diagram?
All of the ions will become surrounded by solvent molecules as the surface disappears
into the solution.
11. When a compound cannot be solvated to any significant extent, it is called
insoluble
_________________________
.
12. Circle the letter next to the one sentence that best explains why the ionic
compounds barium sulfate (BaSO4) and calcium carbonate (CaCO3) are nearly
insoluble in water.
a. The attractions between the ions in the crystals of these ionic compounds
are weaker than the attractions between the ions and water molecules.
b. The attractions between the ions in the crystals of these ionic compounds
are stronger than the attractions between the ions and water molecules.
d. These ionic compounds are easily dissolved in water.
13. What saying sums up the observation that, as a rule, polar solvents dissolve
ionic compounds and polar molecules, but nonpolar solvents dissolve
“like dissolves like”
nonpolar compounds? __________________________
Electrolytes and Nonelectrolytes (pages 483–485)
14. What types of compounds can carry an electric current in the molten
electrolytes
state or in aqueous solution? __________________________
15. Is the following sentence true or false? All ionic compounds are electrolytes.
true
__________________________
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c. There is no difference in the strength of the attractions between the ions in
the crystals and the attractions between the ions and water molecules.
Name ____________________________________ Date __________ Class ___________________
16. Compounds that do not conduct an electric current in either aqueous solution
nonelectrolytes
or the molten state are called __________________________
.
Look at the light bulbs in Figure 17.14 on page 484 to answer Questions 17, 18, and 19.
c
_______
17. Which bulb, a, b, or c, indicates that the solution is nonconductive?
b
_______
18. Which bulb, a, b, or c, indicates that the solution is weakly conductive?
a
_______
19. Which bulb, a, b, or c, indicates that the solution is highly conductive?
Water of Hydration (pages 485–488)
20. Water in a crystal that is an integral part of the crystal structure is called
water of hydration
___________________________
.
21. A compound that contains water as an integral part of its crystal structure is
a hydrate
called _________________________
.
22. What does “5H2O” mean when included in a chemical formula?
The compound contains five water molecules per formula unit.
23. Circle the letter next to each sentence that is true about hydrated compounds.
Use Figures 17.15 and 17.16 on page 486 to help you.
a. Crystals of copper sulfate pentahydrate always contain five molecules of
water for each copper and sulfate ion pair.
b. Heating blue crystals of copper sulfate pentahydrate above 100 °C drives off
the water of hydration, leaving a white anhydrous powder.
c. It is possible to regenerate copper sulfate pentahydrate by treating
anhydrous copper sulfate with water.
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d. Anhydrous cobalt(II) chloride is a good indicator for the presence of water
because it changes from pink to blue when exposed to moisture.
24. If a hydrate has a vapor pressure greater than that of the water in the
effloresce
surrounding air, the hydrate will lose water to the air, or ________________________
.
25. Hygroscopic substances that remove water from the air are used as drying
desiccants
agents called __________________________
.
26. Look at Figure 17.17 on page 487. What happens to dry sodium hydroxide
pellets that are exposed to normally moist air? What kind of compound
exhibits this behavior?
The sodium hydroxide pellets remove enough water from the air to dissolve
completely and form a solution. Sodium hydroxide is an example of a deliquescent
compound.
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CHAPTER 17, Water and Aqueous Systems (continued)
Reading Skill Practice
By looking carefully at photographs and drawings in your textbook, you can better understand what
you have read. Look carefully at Figure 17.13 on page 483. What important idea does this
photograph communicate? Do your work on a separate sheet of paper.
Students should recognize that oil spills cause environmental problems because the insoluble oil
spreads out across the water. As it spreads, it can come into contact with plants and animals.
Oil clogs pores and does other damage to the life cycle of living organisms.
SECTION 17.4 HETEROGENEOUS AQUEOUS SYSTEMS (pages 490–493)
This section describes how colloids and suspensions differ from solutions and explains the
Tyndall effect.
Suspensions (page 490)
1. Is the following sentence true or false? Heterogeneous mixtures are not true
true
solutions. ____________________
2. Heterogeneous mixtures in which particles settle out upon standing are called
suspensions
___________________________
.
3. Is the following sentence true or false? When a suspension of clay particles in
water is filtered, both clay and water will pass through the filter paper.
false
____________________
Colloids (pages 490–493)
5. The scattering of light in all directions by colloidal particles is known as the
Tyndall effect
__________________________
.
6. Identify each type of system shown in the figure below.
Light source
Solution
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Colloid
Suspension
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4. Heterogeneous mixtures in which particles are of intermediate size
colloids
between those of true solutions and suspensions are called ___________________
.